In a typical cellular radio system, wireless terminals (also known as mobile stations and/or user equipment units (UEs)) communicate via a radio access network (RAN) to one or more core networks. User equipment units (UE) may include mobile telephones (“cellular” telephones) and/or other processing devices with wireless communication capability, such as, for example, portable, pocket, hand-held, laptop computers, which communicate voice and/or data with the RAN.
The RAN covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks is also called a “NodeB” or enhanced NodeB “eNodeB”. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. The base stations communicate over the air interface operating on radio frequencies with UEs within range of the base stations.
In some versions of the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a radio network controller (RNC). The radio network controller, also sometimes termed a base station controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Global System for Mobile Communications (GSM), and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UTRAN, short for UMTS Terrestrial Radio Access Network, is a collective term for the Node B's and Radio Network Controllers which make up the UMTS radio access network. Thus, UTRAN is essentially a radio access network using wideband code division multiple access for user equipment units (UEs).
The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies. In this regard, specifications for the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) are ongoing within 3GPP. The Evolved Universal Terrestrial Radio Access Network (E-UTRAN) comprises the Long Term Evolution (LTE) and System Architecture Evolution (SAE).
FIG. 1 is a simplified block diagram of a Long Term Evolution (LTE) RAN 100. The LTE RAN 100 is a variant of a 3GPP RAM where radio base station nodes (eNodeBs) are connected directly to a core network 130 rather than to radio network controller (RNC) nodes. In general, in LTE the functions of a radio network controller (RNC) node are performed by the radio base stations nodes. Each of the radio base station nodes (eNodeBs) 122-1, 122-2, . . . 122-M communicate with UEs (e.g., UE 110-1, 110-2, 110-3, . . . 110-L) that are within their respective communication service cells. The radio base station nodes (eNodeBs) can communicate with one another through an X2 interface and with the core network 130 through S1 interfaces, as is well know in the art.
The LTE standard is based on multi-carrier based radio access schemes such as Orthogonal Frequency-Division Multiplexing (OFDM) in the downlink and single carrier (SC)-FDMA in the uplink. The OFDM's spread spectrum technique distributes the data over a large number of carriers that are spaced apart at precise frequencies. This spacing provides the “orthogonality” in this technique which prevents the demodulators from seeing frequencies other than their own. The benefits of OFDM are high spectral efficiency, resiliency to RF interference, and lower multi-path distortion.
A LTE frame can include both downlink portion(s) and uplink portion(s) that are communicated between the base station and UEs. Each LTE frame can include plural subframes, which may each have a 1 ms duration. FIG. 2 illustrates a resource grid for frequency and time resource elements (REs), where frequency subcarriers (e.g., each having 180 kHz frequency bandwidth) are can be assigned to a plurality of UEs for transmitting and/or receiving data with an associated radio base station node eNodeB during assigned subframes (e.g., each having a 1 ms width).
One or more resource schedulers in the LTE RAN 100 assigns the REs for downlink communications (e.g., the downlink shared channel (DL-SCH)) and for uplink communications (e.g., the uplink shared channel (UL-SCH)). The assignments for downlink shared channel (DL-SCH) and uplink shared channel (UL-SCH) are transmitted in a few OFDM symbols at the beginning of each downlink subframe.
The number of rules and metrics that should be considered by LTE and other RAN resource schedulers has substantially increased their processing demands and challenged their ability to efficiently manage resource elements. These resource schedulers are further stressed by demands for dynamic decision making to provide high bit rate packet switched services simultaneous with providing delay sensitive services, such as voice calls, and to make these decisions while adjusting to changing radio conditions to provide increased air interface data capacity. Accordingly, there is a continuing need to develop improved resource schedulers that can process increased numbers of scheduling rules and metrics to provide efficient resource scheduling.